Hydroxycitric acid derivatives

ABSTRACT

Ester and amide derivatives of threo-hydroxycitric acid γ-lactone inhibit fatty acid synthesis in biological systems and are useful in the treatment of obesity and in correcting conditions of lipid abnormalities.

This is a division of application Ser. No. 376,478, filed July 5, 1973,now U.S. Pat. No. 3,919,254 issued Nov. 11, 1975 which in turn is adivision of application Ser. No. 204,288, filed Dec. 2, 1971, now U.S.Pat. No. 3,767,678, issued Oct. 23, 1973.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to novel compounds of the formula ##STR1##wherein R₁ is hydrogen or lower alkanoyl; Y is one of the groups OR₂ 'or NR₃ R₄ ; Z is one of the groups OR₂ or NR₅ R₆ ; where R₂ is hydrogen,lower alkyl, aryl lower alkyl or aryl; R₂ ' is lower alkyl, aryl loweralkyl or aryl; R₃, R₄, R₅ and R₆ each taken independently is hydrogen,lower alkyl, cycloalkyl, aryl or aryl lower alkyl; R₃ and R₄ takentogether with the adjacent nitrogen atom and R₅ and R₆ taken togetherwith the adjacent nitrogen atom each independently form a 5- or6-membered heterocyclic ring which may contain one additional heteroatomselected from the group consisting of nitrogen and oxygen;

And the optical antipodes and pharmaceutically acceptable salts thereof.

As used throughout the specification and the appended claims, the term"alkyl" shall mean a straight or branched chain hydrocarbon groupcontaining no unsaturation and having up to 20 carbon atoms such asmethyl, ethyl, hexyl, isopropyl, tert.-butyl, decyl, and so forth; theterm "cycloalkyl" shall mean a saturated hydrocarbon group possessing atleast one carbocyclic ring, said ring containing from 3 to 8 carbonatoms such as cyclopropyl, cyclopentyl, cyclohexyl, cyclooctyl,1-adamantyl and so forth; the term "aryl" shall mean phenyl or phenylmonosubstituted with one of the following groups: halogen (i.e.,chlorine, bromine, iodine or fluorine), lower alkyl, hydroxy, loweralkoxy, nitro, cyano, carboxyl or alkanoyl-amino. The term "alkanoyl"shall mean the residue formed by removing the hydroxyl portion from thecarboxyl group of an alkanoic acid having up to 20 carbon atoms, such asformyl, acetyl, propionyl, pivaloyl, hexanoyl, and so forth. Examples ofheterocyclic rings formed when R₃ and R₄ or R₅ and R₆ are taken togetherwith the adjacent nitrogen atom are pyrrolidinyl, piperidinyl,morpholinyl and so forth. The term "lower" as applied to any of theforegoing groups denotes a group having a carbon skeleton containing upto and including 8 carbon atoms.

The compounds of formulas Ia and Ib are prepared by a novel sequence ofreactions depicted in Reaction Scheme A. The starting material for thisreaction sequence is racemic or optically active threo-hydroxycitricacid γ-lactone (II). The (+)-antipode of formula II is a well knownnatural product, Garcinia acid, obtainable by isolation from the fruitof Garcinia cambogia using known procedures.

It should be understood that the processes described herein may beemployed either in the racemic or in the optically active series andthat all of the novel compounds described herein may be prepared in theracemic or in either antipodal form. Where an optically active startingmaterial of formula II is not utilized, suitable intermediates such asthose of formula Ia can be resolved utilizing standard opticalresolution techniques involving the separation of diastereomeric saltsof the acid with an optically active base.

The novel compounds of the present invention may be convenientlyprepared via the intermediate anhydride III. The anhydride is preparedfrom threo-hydroxy citric acid γ-lactone II by treatment of the latterwith an anhydrating agent. An anhydrating agent is defined as an agentwhich serves to convert a cis-1,2-dicarboxylic acid to the correspondinganhydride. Suitable anhydrating agents include alkanoic acid anhydrides,for example acetic anhydride, propionic anhydride and so forth; andalkanoyl halides, for example acetyl chloride, propionyl chloride, andso forth. ##STR2## The anhydrating agent effects both the conversion ofthe cis-dicarboxylic acid grouping to an anhydride and the conversion ofthe hydroxyl group to its lower alkanoyl derivative. Thus, the alkanoylportion of the anhydrating agent is retained as R₁ of the anhydride III.

The formation of the anhydride III may be conveniently carried out usingan excess of the anhydration agent as the reaction medium, although aninert organic solvent may be employed as a diluent. Suitable inertorganic solvents include hydrocarbons, e.g. benzene or toluene; organicethers, e.g. dioxane or ethylene glycol dimethyl ether and so forth.

The anhydration reaction is suitably carried out at an elevatedtemperature in the range of from about 50° to about 150° C., mostpreferably from about 80° to about 120° C. In a particularly preferredprocedure, a mixture of alkanoic acid anhydride and alkanoyl halidederived from the same alkanoic acid is employed as an anhydrating agent.The ratio of these reagents is not narrowly critical and a mole ratio offrom about 1:9 to about 9:1 anhydride:halide is operable. A ratio offrom about 1:2 to about 2:1 anhydride:halide is preferred.

The anhydride III is an excellent acylating agent for amines andalcohols. Thus, the anhydride III can be reacted either with an alcoholof the formula R₂ 'OH, where R₂ ' is as above, with an amine of theformula R₃ R₄ NH, where R₃ and R₄ are as above, to afford, respectively,compounds of formula Ia-1 and Ia-2. ##STR3##

Wherein R₁, R₂ ', R₃ and R₄ are as above. The compounds prepareddirectly from the anhydride III are those members of the subgenuses Ia-1and Ia-2 wherein R₁ is lower alkanoyl. The preparation of the remainingmembers of these subgenuses wherein R₁ is hydrogen is described below.This also applies for the preparation of compounds of formula Ib.

The reaction is suitably effected by treating the anhydride with anexcess of either the amine or alcohol in an inert organic solvent. Whenan amine is used as a reactant, it is generally preferred to utilize atleast 2 equivalents since one equivalent will react with the carboxylgroup generated to form an addition salt. Suitable inert organicsolvents include hydrocarbons, e.g. benzene, toluene, hexane and soforth; organic ethers, e.g. diethyl ether, tetrahydrofuran, dioxane andso forth; and the like. The acylation reaction may be carried out withina temperature range of from about -20° to about 150° C. A temperaturerange of from about 0° to 30° C. is preferred for amines and lowermolecular weight alcohols. A temperature range of 75° to 100° C. ispreferred for higher molecular weight alcohols.

The monosubstituted compounds of formula Ia can be converted to thedisubstituted compounds of formula Ib in a two-step process comprisingconversion of the free-carboxyl group to an active derivative such as anacyl halide, mixed anhydride or acyl imidazole, followed by reaction ofthis activated derivative with either an alcohol of the formula R₂ "OHor an amine of the formula R₅ R₆ NH. Compounds of formula Ia-1 are thusconverted to compounds of formula Ib-1 and Ib-2, respectively. ##STR4##

where R₁, R₂ ', R₂ ", R₅ and R₆ are as above. Compounds of formula Ia-2are converted in this manner to compounds of formulas Ib-3 and Ib-4,respectively. ##STR5## where R₁, R₂ ', R₂ ", R₃, R₄, R₅ and R₆ are asabove.

Acyl halides of the carboxylic acids of formula Ia may be prepared byreacting the carboxylic acid with a suitable halogenating agent.Examples of suitable halogenating agents are, for example, thionylchloride, oxalyl chloride, thionyl bromide, phosphorus trichloride,phosphorous tribromide and so forth. The acyl halides are prepared byreacting the carboxylic acid and halogenating agent in an inert organicsolvent. Suitable inert organic solvents include hydrocarbons, e.g.benzene and toluene; organic ethers, e.g. diethyl ether, tetrahydrofuranand so forth. The halogenation reaction may be conveniently carried outat a temperature of from about 20° to about 150° C. A temperature offrom about 50° to about 150° C. is preferred. The carboxylic acids offormula Ia can also be converted to other activated acyl derivativessuch as acyl imidazoles. In this process, the carboxylic acid is treatedwith carbonyl diimidazole in an inert organic solvent at about roomtemperature.

The activated acyl derivatives described above are next reacted with theappropriate alcohol or amine to afford the compounds of formula Ib. Thisreaction may be carried out conveniently in an inert organic solventsuch as hydrocarbons, e.g. benzene or toluene; organic ethers, e.g.diethyl ether, tetrahydrofuran or dioxane; organic esters, e.g. ethylacetate; and the like. The reaction temperature may range from about 0°to about 100° C; although, a temperature of from about 0° to about roomtemperature is generally preferred.

Compounds of formula Ib-1 and Ib-3 wherein R₂ " is lower alkyl or aryllower alkyl, may be prepared by reacting the carboxylic acid with theappropriate diazoalkylene or phenyl diazoalkylene, e.g. diazomethane,diazoethane or phenyl diazomethane in an inert organic solvent,preferably in an organic ether, at about room temperature.

In another aspect of the present invention, compounds Ia and Ib areconverted to compounds of formulas IV-a and IV-b, respectively, bytreatment with an alcohol, R'OH, where R' is as above, in the presenceof a strong acid. In this reaction, alkanoylsis of the lactone ring, andconcomitant esterification of the free carboxyl group as well ashydrolysis of the ester OR₁ occurs. The reaction is conveniently carriedout in any suitable inert organic solvent, although, it is generallypreferred to employ an excess of the alcohol reactant as the solvent.Suitable strong acids include mineral acid, e.g. hydrochloric acid,hydrobromic acid, sulfuric acid and so forth; organic sulfonic acids,e.g. p-toluene sulfonic acid and so forth; and the like. The strong acidmay either be added directly to the reaction mixture or may be generatedin situ by reaction of a suitable acid precursor with the alcoholpresent. Suitable acid precursors include the halogenating agentsdescribed above for the preparation of the acyl halides, such as thionylchloride or oxalyl chloride. The alcoholysis reaction may be carried outat a temperature range of from about room temperature to about 100° C.It is particularly convenient to carry out the reaction at the boilingpoint of the reaction medium. Compounds of formulas IVa-1 and IVb-1##STR6## wherein R', R₃ and R₄ are as above, Y' is one of the groups OR₂' or NR₃ R₄, where R₂, R₃ and R₄ are as above, Z" is one of the groupsOR₂ " or NR₅ R₆, wherein R₂ " is lower alkyl, aryl lower alkyl or aryland R₅ and R₆ are as above, but with the added proviso that Y' cannot beOR₂ ' when Z" is OR_(2"),

are novel and are useful in controlling lipogenesis.

Compounds of formulas Ia and Ib wherein R₁ is hydrogen may be preparedfrom compounds IVa and IVb, respectively, by lactonization. Suitablelactonization procedures include heating the compound of formula Ia orIb with azeotropic removal of R'OH. A particularly preferred procedureis fractional distillation.

The compounds of formulas I and IV are useful for inhibiting fatty acidsynthesis in biological systems. The biological systems in which thecompounds of the present invention may be used include those containingcitrate cleavage enzyme. Preferred biological systems are mammals,particularly non-ruminating mammals.

The inhibition of fatty acid synthesis in biological systems by the useof the compounds of the present invention is believed to arise from theinhibition by such compounds of citrate cleavage enzyme contained insuch systems. The cleavage of citrate is catalyzed by citrate cleavageenzyme according to the stoichiometry: citrate + CoA + ATP → acetyl -CoA + oxaloacetate + ADP + P_(i).

In the conversion of carbohydrates and various amino acids to fat bynon-ruminating mammals, citrate is the major source of acetyl co-enzymeA, which is utilized for the synthesis of fatty acids. Citrate is formedin the mitochondria by the citrate synthase reaction. It is thenmetabolized via the citric acid cycle. Under conditions when energyintake exceeds energy demand, some citrate is diverted to theextra-mitochondrial space of the cell where it is used for fatty acidsynthesis, that is to say, for energy storage. The novel compounds offormulas I and IV of the present invention are thus useful in thetreatment of obesity and in the correction of lipid abnormalities.

As mentioned above, compounds of formula I may be used in the form ofpharmaceutically acceptable salts. Preferred salts for this purposeinclude alkali metals, e.g. sodium or potassium the alkaline earthmetals, e.g. calcium; or complex salts such as ammonium or substitutedammonium salts such as a mono-, di- or tri-alkylammonium salt or amono-, di- or tri-hydroxyalkyl-ammonium salt.

These compounds can be made up in the form of conventionalpharmeceutical preparations; for example, the aforesaid compounds can bemixed with organic or inorganic inert pharmaceutical carriers suitablefor parenteral or enteral administrations such as, for example, water,gelatin, lactose, starch, magnesium stearate, talc, vegetable oil, gumsor the like. They can be administered in conventional pharmaceuticalforms, e.g. solid forms, for example, tablets, capsules, dragees,suppositories, or the like; or in liquid forms, for example, solutions,suspensions, or emulsions. Moreover, the pharmeceutical compositionscontaining the compounds of this invention can be subjected to theconventional pharmaceutical expedients such as sterilization, and cancontain conventional pharmaceutical excipients such as preservatives,stabilizing agents, emulsifying agents, salts for the adjustment ofosmotic pressure or buffers. The compositions can also contain othertherapeutically active materials.

A suitable pharmaceutical dosage unit can contain from about 15 to 600mg. of the aforesaid compound. Suitable parenteral dosage regimens inmammals comprise from about 1 mg/kg to about 25 mg/kg per day. However,for any particular subject, specific dosage regimens should be adjustedaccording to the individual need and the professional judgment of theperson administering or supervising the administration of the aforesaidcompounds. It is to be understood that the dosages set forth herein areexemplary only and that they do not, to any extent, limit the scope orpractice of the invention.

The present invention may be more clearly illustrated by the followingexamples. All the temperatures are stated in degrees centigrade.

EXAMPLE 1 2(S),3(S)-Tetrahydro-3-acetoxy-5-oxo-furan-2,3-dicarboxylicacid anhydride

A. A mixture of (+)-threo-hydroxycitric acid γ lactone [2(S),3(S)-tetrahydro-3-hydroxy-5-oxo-furan-2,3-dicarboxylic acid,(+)-Garcinia acid] (28.0 g.) and acetic anhydride (150 ml.) wasmaintained at 95° (steam bath) for 30 minutes, then the solvent wasremoved under reduced pressure. A solution of the residue in methylenechloride was filtered to remove a small amount of insoluble materialthen was diluted with carbon tetrachloride. The resulting crystallineprecipitate was collected by filtration to give 26.1 g. of theanhydride, mp 136° - 139°. Recrystallization from methylenechloride-ether furnished the analytical sample, mp 142° - 143°.

B. A solution of (+)-threo-hydroxycitric acid γ lactone (20 g.) inacetic anhydride (80 ml.) and acetyl chloride (40 ml.) was heated atreflux under anhydrous conditions for 90 minutes. The solvent wasremoved in vacuo to give 22 g. of the anhydride identical with thatprepared in part A. above.

Anal. Calcd. for C₈ H₆ O₇ : C, 44.87; H, 2.82 Found: C, 44.26; H, 2.98.

EXAMPLE 22(S),3(S)-Tetrahydro-2-methoxycarbonyl-3-acetoxy-5-oxo-3-furancarboxylicacid

The anhydride, prepared as in Example 1, (11.09 g.) was dissolved inanhydrous methanol (100 ml.) and heated to reflux for 5 minutes. Thesolvent was removed under reduced pressure and the resulting solid wasdried under high vacuum. Crystallization from dry chloroform-carbontetrachloride afforded 11.2 g. of the monoester, mp 116° - 118°. Theanalytically pure sample was obtained from dry chloroform-hexane, mp116° - 118°; [α]_(D) ²⁵ + 110.65°(c, 1.0, CHCl.sub. 3).

Anal. Calcd. for C₉ H₁₀ O₈ : C, 43.91; H, 4.09 Found: C, 43.86; H, 4.28.

EXAMPLE 32(S),3(S)-Tetrahydro-2-ethoxycarbonyl-3-acetoxy-5-oxo-3-furancarboxylicacid

The anhydride, prepared as in Example 1, (6.5 g.) was dissolved inabsolute ethanol (100 ml.) and heated to reflux for five minutes. Thesolvent was evaporated in vacuo to give 8.0 g. of a white solid.Crystallization from ether-hexane furnished 4.7 g. of the ethyl ester,m.p. 133° - 135°. Concentration of the mother liquors gave an additional2.0 g., mp 132° - 134°. Recrystallization from ether-hexane afforded thepure material, mp 135° - 136°; [α]_(D) ²⁵ + 110.98° .

Anal. Calcd. for C₁₀ H₁₃ O₇ : C, 46.16; H, 4.65 Found: C, 46.03; H,4.57.

EXAMPLE 4 Methyl2(S),3(S)-tetrahydro-3-acetoxy-3-carbamoyl-5-oxo-2-furancarboxylate

Oxalyl chloride (20 ml.) was added to a solution of the methyl ester,prepared as in Example 2, (6.2 g.) in dry tetrahydrofuran and thesolution was refluxed for 30 minutes. The solution was evaporated invacuo and residual oxalyl chloride was removed by repeated evaporationwith dry benzene. The residual acid chloride was dissolved in drytetrahydrofuran (50 ml.) and the solution was cooled to 0°. To thisstirred solution, 25 ml. of a 2.3 M solution of ammonia intetrahydrofuran was added rapidly. After 1 minute the solvent wasremoved under reduced pressure and the resulting oil was dissolved inwater and extracted into ethyl acetate. The combined organic extractswere dried (Na₂ SO₄) and concentrated to dryness to give 4.8 g. of crudeamide as an oil. Crystallization from ethyl-hexane afforded 2.3 g. ofthe amide as a yellow solid, mp 161° - 163°. Concentration of the motherliquors gave an additional 1.2 g. of material, mp 160° - 163 °. Thecombined crops were decolorized with charcoal and crystallized fromethyl acetate-hexane to give 2.8 g. of colorless crystals, mp 164° -166°. The analytically pure material was obtained from the same solventsystem, mp 165° - 166°, [α]_(D) ²⁵ + 129.42° (c, 1.0, MeOH).

Anal. Calcd. for C₉ H₁₁ NO₇ : C, 44.09; H, 4.52; N, 5.71 Found: C,44.03; H, 4.58; N, 5.49.

EXAMPLE 5 Ethyl2(S),3(S)-tetrahydro-3-acetoxy-3-carbamoyl-5-oxo-2-furanacarboxylate

A mixture of ethyl ester, prepared as in Example 3, (15 g.) and oxalylchloride (60 ml.) was heated at reflux for 60 minutes then the solventwas removed in vacuo and the residual oxalyl chloride was eliminatedthrough repeated evaporation with dry benzene. The crude acid chloridewas dissolved in dry tetrahydrofuran and the solution was cooled in anice-water bath then 80 ml. of a 2.3M solution of ammonia intetrahydrofuran was added rapidly. The solution was evaporatedimmediately in vacuo at low temperature and the residue was dissolved inwater and extracted with ethyl acetate. The organic extracts were dried(Na₂ SO₄) and concentrated under reduced pressure to give 13 g. of crudeamide as a yellow oil. Crystallization from ethyl acetatehexanefurnished 9.8 g. of yellow crystals, mp 133° - 135°. Decolorizationusing charcoal and subsequent recrystallization from ethyl acetateafforded analytically pure amide, mp 134° - 5°, [α]_(D) ²⁵ + 108.84° (c,1.0, CHCl.sub. 3).

Anal. Calcd. for C₁₀ H₁₃ NO₇ : C, 46.34; H, 5.06; N, 5.40. Found: C,46.12; H, 5.06; N, 5.24.

EXAMPLE 62(S),3(S)-Tetrahydro-2-(N-ethylcarbomoyl)-3-acetoxy-5-oxo-3-furancarboxylicacid

A stirred solution of 78 mmol anhydride, prepared as in Example 1, indry tetrahydrofuran (150 ml.) was treated with a solution ofmonoethylamine (8 g; 0.176 mol) in anhydrous tetrahydrofuran. Theexothermic reaction was moderated by cooling in an ice-water bath. After5 minutes the solvent was removed in vacuo and the residue was taken upin 1 N hydrochloric acid (180 ml.). The acidic mixture was extractedwith ethyl acetate (2 x) and the organic extracts were washed withbrine. The combined ethyl acetate layers were dried (Na₂ SO₄) andconcentrated in vacuo to give 14.1 g. of a solid residue.Crystallization from ethyl acetate-carbon tetrachloride furnished 9.7 g.of the white crystalline amide, mp 161° - 3°. The analytically purematerial was obtained from the same solvent mixture, mp 161° - 3°;[α]_(D) ²⁵ + 143.75° (c, 1.02, MeOH).

Anal. Calcd. for C₁₀ H₁₃ NO₇ : C, 46,34; H, 5.06; N, 5.40 Found: C,46.07; H, 5.24; N, 5.46.

EXAMPLE 72(S),3(S)-Tetrahydro-2-[N-(1-adamantylcarbamoyl)]-3-acetoxy-5-oxo-3-furancarboxylicacid

To a stirred solution of anhydride, prepared as in Example 1, (9.8 g;51.5 mmol) in dry tetrahydrofuran (250 ml.) was added a solution of 1-adamantanamine (16.8 g; 0.11 mol) in anhydrous tetrahydrofuran (100ml.). After five minutes the solvent was removed in vacuo and theresidue was dispersed in 1 N hydrochloric acid solution (150 ml.). Themixture was extracted with chloroform (3 x) and the organic layers werewashed in turn with 2% hydrochloric acid solution (1 x) and with brine(2 x). The combined extracts were dried (MgSO₄) and evaporated underpressure. The residue was crystallized twice from acetonehexane to give17.7 g. of the amide, mp 129°-131° (dec). Recrystallization fromacetone-hexane afforded the analytical sample as the acetone solvate, mp130° (dec); [α]_(D) ²⁵ + 65.3° (c, 0.5, CHCl₃).

Anal. Calcd. for C₁₈ H₂₃ NO₇.sup. . 3/4 C₃ H₆ O: C, 59.52; H, 6.78; N,3.43 Found: C, 59.71; H, 6.98; N, 3.33.

EXAMPLE 83(S),2(S)-Tetrahydro-2-(N,N-diethylcarbamoyl)-3-acetoxy-5-oxo-3-furancarboxylicacid

A solution of diethylamine (12.5 ml; 0.12 mol) in anhydroustetrahydrofuran (100 ml.) was added rapidly to a stirred solution of5.25 mmol of the anhydride, prepared as in Example 1, in drytetrahydrofuran (100 ml.). The reaction was cooled throughout by meansof an ice-water bath. After five minutes the reaction mixture wasconcentrated under reduced pressure and the resulting material wasdissolved in 1 N hydrochloric acid solution (100 ml.). The acidicreaction mixture then was extracted with ethyl acetate (2 x) and theorganic layers were washed with 0.2 N hydrochloric acid. The combinedextracts were dried (MgSO₄) and decolorized using charcoal and then wereevaporated to dryness in vacuo. The residue was recrystallized twicefrom methylene chloride-hexane to give 8.1 g. of pure diethylamide, mp132°-3° (dec); [α]_(D) ²⁵ + 64.62° (c, 0.89, CHCl₃).

Anal. Calcd. for C₁₂ H₁₇ NO₇ : C, 50.17; H, 5.96; N, 4.88 Found: C,49.61; H, 5.95; N, 4.79.

EXAMPLE 9 Ethyl3(S),4(S)-4-[N-(1-adamantylcarbamoyl)]-3-ethoxycarbonyl-3,4-dihydroxybutanoate

A solution of the amide acid, prepared as in Example 7, (1.0 g.) andoxalyl chloride (2 ml.) in absolute ethanol (30 ml.) was refluxed for 1hour and then left at room temperature overnight. The reaction mixturewas poured into sodium bicarbonate solution and extracted with ethylacetate (2 x). The organic layers were washed in turn with brine, dilutehydrochloric acid solution, dilute sodium bicarbonate solution andfinally brine. The combined extracts were dried (MgSO₄) and concentratedto dryness under reduced pressure. Two crystallizations from ethylacetate furnished 575 mg. of pure diol diester, mp 115°-6°. Theanalytically pure material was obtained from the same solvent mixture,mp 116°-7°; [α] - 18.35° (c, 0.98, CHCl₃).

Anal. Calcd. for C₂₀ H₃₁ NO₇ : C, 60.44; H, 7.89; N, 3.52 Found: C,60.09; H, 7.76; N, 3,41.

EXAMPLE 10 Methyl2(S),3(S)-tetrahydro-2-(N,N-diethylcarbamoyl)-3-acetoxy-5-oxo-3-furancarboxylate

A cooled solution of amide acid, prepared as in Example 8, (60.0 g.) indiethyl ether (125 ml.) was treated with a solution of diazomethane inether until the yellow color persisted. The solution was left at roomtemperature until the excess diazomethane dissipated then the solventwas removed in vacuo. The resulting residue was crystallized twice fromether to yield 3.45 g. of the pure methyl ester, mp 103.5°-105°; [α]_(D)²⁵ + 68.68° (c, 0.99, CHCl₃).

Anal. Calcd. for C₁₃ H₁₉ NO₇ : C, 51.82; H, 6.36; N, 4.65 Found: C,51.71; H, 6.41; N, 4.59.

EXAMPLE 11 Diethyl2(S),3(S)-tetrahydro-3-acetoxy-5-oxo-2,3-furan-dicarboxylate

A solution of the monoethyl ester, prepared as in Example 3, (1.0 g.)and oxalyl chloride (4 ml.) in tetrahydrofuran (20 ml.) was heated at areflux for 30 minutes then the solvent was removed under reducedpressure. The acid chloride was dissolved in 10 ml. of absolute ethanoland after several minutes the solvent was again removed in vacuo. Thecrude diester was dissolved in ethyl acetate and the solution was washedwith aqueous sodium bicarbonate and with brine. The dried (MgSO₄)organic layer was concentrated to dryness in vacuo to give 530 mg. ofthe diester as an oil. This material was decolorized (charcoal) andcrystallized (3 x) from chilled ether-hexane solutions to give 230 mg.of the analytically pure diethyl ester, mp 39°-40°, [α]_(D) ²⁵ + 97.5°(c, 1.04, CHCl₃).

Anal. Calcd. for C₁₂ H₁₆ O₈ : C, 50.00; H, 5.59 Found: C, 50.09; H,5.61.

EXAMPLE 12 Ethyl2(S),3(S)-tetrahydro-3-(N-ethylcarbamoyl)-3-acetoxy-5-oxo-2-furancarboxylate

A solution of the monoester, prepared as in Example 3, (1.0 g; 3.9 mmol)in dry tetrahydrofuran (20 ml.) containing oxalyl chloride (4 ml.) wasrefluxed for thirty minutes then was evaporated to dryness under reducedpressure. The residue was dissolved in dry tetrahydrofuran (20 ml.) andcooled to 0°-5° by means of a ice-water bath. To the stirred solutionmonoethylamine (346 mg; 7.8 mmol) in tetrahydrofuran (5 ml.) was addedin one portion. After five minutes the reaction mixture was diluted withwater and extracted with ethyl acetate (3 x). The ethyl acetate extractswere washed in turn with sodium bicarbonate solution (2 x) and brine (3x), then were combined, dried (MgSO₄) and evaporated in vacuo to give0.9 g. of product. Crystallization of the crude material fromchloroform-hexane afforded 720 mg. of the ethylamide, mp 131°-2°.Recrystallization from ethyl acetate-carbon tetrachloride furnished theanalytically pure material, mp 134°-5°; [α]_(D) ²⁵ + 101.26° (c, 1.035,CHCl₃).

Anal. Calcd. for C₁₂ H₁₇ NO₇ : C, 50.17; H, 5.96; N, 4.88 Found: C,50.20; H, 6.10; N, 4.84.

EXAMPLE 13 Ethyl2(S),3(S)-tetrahydro-3-(N,N-diethylcarbamoyl)-3-acetoxy-5-oxo-2-furancarboxylate

A solution of the monoester, prepared as in Example 3, (10 g; 39 mmol)in tetrahydrofuran (100 ml.) containing oxalyl chloride (40 ml.) washeated at reflux temperature for thirty minutes then the solvent wasremoved into vacuo. The crude acid chloride was dissolved intetrahydrofuran (100 ml.) and to the cooled solution (0°-5°)diethylamine (10 ml; 96 mmol) was added. After 5 minutes the reactionmixture was diluted with water and extracted with ethyl acetate (3 x).The organic extracts were washed with sodium bicarbonate solution (3 x)and with brine (3 x) then were combined, dried (MgSO₄) and evaporated.The residue was crystallized from ether to give 5.3 g. of thediethylamide, mp 81°-82°. The analytically pure material was obtainedfrom the same solvent, mp 81°-82°; [α]_(D) ²⁵ + 136.79° (c, 0.935,CHCl₃).

Anal. Calcd. for C₁₄ H₂₁ NO₇ : C, 53.33; H, 6.71; N, 4.44 Found: C,53.47; H, 4.41.

EXAMPLE 14 Ethyl2(S),3(S)-tetrahydro-3-[N-(4-carboxyphenyl)carbamoyl]-3-acetoxy-5-oxo-2-furanacarboxylate

A solution of the monoester, prepared as in Example 3, (7.0 g; 27 mmol)and oxalyl chloride (28 mol) in tetrahydrofuran (140 ml.) were heated atreflux for thirty minutes. The solvent was evaporated to dryness invacuo and the residual oxalyl chloride was removed by the repeatedaddition and evaporation of dry benzene. The crude acid chloride wasdissolved in dry tetrahydrofuran (50 ml.) and to this stirred solution asolution of p-aminobenzoic acid (4.4 g; 32 mmol) and sodium hydroxide(1.32 g; 33 mol) in water (12 ml.) was added in one portion. After 5minutes most of the solvent was removed under reduced pressure and thereaction mixture was diluted with ethyl acetate and washed with dilutehydrochloric acid (2 x) and brine (2 x). The organic layers were dried(MgSO₄) and concentrated to dryness in vacuo. The residue was dispersedin 1 N hydrochloric acid and extracted with chloroform (6 x). Thechloroform extracts were washed with water, then combined, dried (MgSO₄)and evaporated under reduced pressure. Crystallization of the residuefrom ethyl acetate-carbon tetrachloride furnished in two crops 5.0 g. ofproduct, mp 187°, (dec). The analytically pure sample was obtained fromethylacetate-hexane, mp 187° (dec); [α]_(D) ²⁵ + 139.8° (c, 0.9, MeOH).

Anal. Calcd. for C₁₇ H₁₇ NO₉ : C, 53.83; H, 4.52; N, 3.69 Found: C,53.69; H, 4.65; N, 3.69.

EXAMPLE 152(S),3(S)-Tetrahydro-2-benzyloxycarbonyl-3-acetoxy-5-oxo-3-furancarboxylicacid

To a solution of 15.8 mmol of the anhydride, prepared as in Example 1,in tetrahydrofuran (75 ml.) was added benzyl alcohol, (1.8 ml; 17.4mmol) followed by pyridine (1.5 ml; 18.6 mmol). The solution was left atroom temperature for two hours then most of the solvent was removed invacuo. The residue was dissolved in water and washed with ether (2 x).The aqueous layer was acidified with 1 N hydrochloric acid solution (20ml.) and extracted with chloroform. Evaporation of the dried (Na₂ SO₄)chloroform extracts furnished an oil. Crystallization frommethanol-water afforded 3.5 g. of product as its monomethanol solvate,mp 79°-81.5°, [α]_(D) ²⁵ + 93.7° (c, 0.5, MeOH).

Anal. Calcd. for C₁₅ H₁₄ O₈.sup. . CH₃ OH: C, 54.24; H, 5.12 Found: C,54.48; H, 5.21.

EXAMPLE 16 Diethylammonium2(S),3(S)-tetrahydro-2-benzyloxycarbonyl-3-acetoxy-5-oxo-3-furancarboxylate

Diethylamine (1.65 ml; 16 mmol) was added to a solution of crude benzylester, prepared as in Example 15, (4.0 g; 12.5 mmol) and a whitecrystalline material began to form immediately. The solid was collectedby filtration and washed with ether to give 4.0 g. of salt.Recrystallization from methanol-ether furnished 3.4 g. of thediethylammonium derivative, mp 128°-130°; [α]_(D) ²⁵ + 101.81° (c, 0.94,CH₃ OH).

Anal. Calcd. for C₁₉ H₂₅ NO₈ : C, 57.71; H, 6.37; N, 3.54 Found: C,58.17; H, 6.41; N, 3.49

The pharmaceutical formulations in Examples 17 - 22 are illustrated for2(S),3(S)-tetrahydro-2-methoxycarbonyl-3-acetoxy-5-oxo-3-furancarboxylicacid. They are applicable to all the compounds of formulas I and IV.

EXAMPLE 17

    ______________________________________                                        Capsule Formulation                                                           ______________________________________                                                              Per Capsule                                             ______________________________________                                        2(S),3(S)-tetrahydro-2-methoxycarbonyl-                                        3-acetoxy-5-oxo-3-furancarboxylic acid                                                               250 mg.                                               Lactose                 60 mg.                                                Corn Starch             35 mg.                                                Magnesium Stearate       5 mg.                                                Total Weight            350 mg.                                               ______________________________________                                    

PROCEDURE

1. all of the ingredients were mixed until thoroughly blended in asuitable size container.

2. The powder was filled into No. 2, two piece, hard shell gelatincapsules to an approximate fill weight of 350 mg. using a Parke Daviscapsulating machine. (Any similar type machine may be used.)

EXAMPLE 18

    ______________________________________                                        Tablet Formulation                                                            ______________________________________                                                              Per Tablet                                              ______________________________________                                        2(S),3(S)-tetrahydro-2-methoxycarbonyl-                                        3-acetoxy-5-oxo-3-furancarboxylic acid                                                               200 mg.                                               Dicalcium Phosphate Dihydrate, Unmilled                                                               235 mg.                                               Corn Starch              70 mg.                                               FD & C Yellow No. 5 - Aluminum Lake 25%                                                                2 mg.                                                Durkee 117               25 mg.                                               Calcium Stearate         3 mg.                                                Total Weight            535 mg.                                               ______________________________________                                    

PROCEDURE

1. all the ingredients were mixed thoroughly and Fitzed (Model D) usinga No. 1A screen, medium speed.

2. The mixture was remixed and slugged.

3. The slugs were screened on an Oscillator through a No. 14 mesh screenand compressed on an "E" machine.

EXAMPLE 19

    ______________________________________                                        Capsule Formulation                                                           ______________________________________                                                              Per Capsule                                             ______________________________________                                        2(S),3(S)-tetrahydro-2-methoxycarbonyl-                                        3-acetoxy-5-oxo-3-furancarboxylic acid                                                               50 mg.                                                Lactose, USP            125 mg.                                               Corn Starch, USP        30 mg.                                                Talc, USP                5 mg.                                                Total Weight            210 mg.                                               ______________________________________                                    

PROCEDURE

1.2(s),3(s)-tetrahydro-2-methoxycarbonyl-3-acetoxy-5-oxo-3-furancarboxylicacid was mixed with lactose and corn starch in a suitable mixer.

2. The mixture was further blended by passing through a FitzpatrickComminuting Machine with a No. 1A screen with knives forward.

3. The blended powder was returned to the mixer, the talc added andblended thoroughly.

4. The mixture was filled into No. 4 hard shell gelatin capsules on aParke Davis capsulating machine.

EXAMPLE 20

    ______________________________________                                        Tablet Formulation                                                            ______________________________________                                                              Per Tablet                                              ______________________________________                                        2(S),3(S)-tetrahydro-2-methoxycarbonyl-                                        3-acetoxy-5-oxo-3-furancarboxylic acid                                                               25 mg.                                                Dicalcium Phosphate Dihydrate, Unmilled                                                               175 mg.                                               Corn Starch             24 mg.                                                Magnesium Stearate       1 mg.                                                Total Weight            225 mg.                                               ______________________________________                                    

PROCEDURE

1.2(s),3(s)-tetrahydro-2-methoxycarbonyl-3-acetoxy-5-oxo-3-furancarboxylicacid and corn starch were mixed together and passed through a No. 00screen in Model "J" Fitzmill with hammers forward.

2. This premix was then mixed with dicalcium phosphate and one-half ofthe magnesium stearate, passed through a No. 1A screen in Model JFitzmill with knives forward, and slugged.

3. The slugs were passed through a No. 2A plate in a Model D Fitzmill atslow speed with knives forward, and the remaining magnesium stearate wasadded.

4. The mixture was mixed and compressed.

EXAMPLE 21

    ______________________________________                                        Tablet Formulation                                                            ______________________________________                                                              Per Tablet                                              ______________________________________                                        2(S),3(S)-tetrahydro-2-methoxycarbonyl-                                        3-acetoxy-5-oxo-3-furancarboxylic acid                                                               100 mg.                                               Lactose, USP            202 mg.                                               Corn Starch, USP         80 mg.                                               Amijel B011*             20 mg.                                               Calcium Stearate         8 mg.                                                Total Weight            410 mg.                                               ______________________________________                                    

PROCEDURE

1.2(s),3(s)-tetrahydro-2-methoxycarbonyl-3-acetoxy-5-oxo-3-furancarboxylicacid, lactose, corn starch, and Amijel BO11 were blended in a suitablemixer.

2. The mixture was granulated to a heavy paste with water and the moistmass was passed through a No. 12 screen. It was then dried overnight at110° F.

3. the dried granules were passed through a No. 16 screen andtransferred to a suitable mixer. The calcium stearate was added andmixed until uniform.

4. The mixture was compressed at a tablet weight of 410 mg. using tabletpunches having a diameter of approximately 3/8 inch. (Tablets may beeither flat or biconvex and may be scored if desired).

EXAMPLE 22

    ______________________________________                                        Tablet Formulation                                                            ______________________________________                                                              Per Tablet                                              ______________________________________                                        2(S),3(S)-tetrahydro-2-methoxycarbonyl-                                        3-acetoxy-5-oxo-3-furancarboxylic acid                                                               500 mg.                                               Corn Starch             30 mg.                                                Lactose                 88 mg.                                                Gelatin                 12 mg.                                                Talcum                  15 mg.                                                Magnesium Stearate       5 mg.                                                Total Weight            650 mg.                                               ______________________________________                                    

PROCEDURE

1.2(s),3(s)-tetrahydro-2-methoxycarbonyl-3-acetoxy-5-oxo-3-furancarboxylicacid and lactose were thoroughly mixed in suitable blending equipmentand granulated with a 10% gelatin solution.

2. The moist mass was passed through a No. 12 screen, and the granuleswere dried on paper lined trays overnight.

3. The dried granules were passed through a No. 14 screen and placed ina suitable mixer. The talcum and magnesium stearate were added andblended.

4. The granulation was compressed into tablets weighing approximately650 mg. each, using punches having an approximate diameter of 12.7 mm.(1/2 inch). The final tablet thickness was about 5.1 mm.

EXAMPLE 23 Measurement of lipogenesis in vivo

Female Charles River rats weighing from 120-150 g. were provided freeaccess to water and were fed a commercial diet prior to the initiationof the experiment. Each experimental group of animals were pre-fastedtwo days and then meal-fed a single meal daily from 9-12 a.m. The mealconsisted of a 70% glucose fat-free diet (G-70) containing 70% glucose,24% vitamin-free casein, 5% salt and 1% vitamins, to which 40 g.cellulose was added per kilogram.

On the last of feeding, at a specified time before initiation of themeal, the hydroxycitric acid derivative in ASV of the composition sodiumchloride 0.9%, carboxy methyl cellulose 0.5%, benzyl alcohol 0.865 andtween 80 (polyoxyethylene sorbitan monoleate) 0.39% was administered. Ata specified time after feeding, rats were lightly anaesthetized withPenthrane (methoxyflurane) and injected in the tail vein with 0.25 ml.of a solution with the following composition: 12.3 mg. alanine, 5μC¹⁴C-alanine (specific activity = 156 mC/mmole) as fatty acid precursor and30.6 mg. α-ketoglutarate as a transaminase acceptor dissolved in salinepH 7.4 - 7.6. After 30 minutes, rats were sacrificed by decapitation andtheir livers were excised, rapidly weighed, minced in 15 ml. water andhomogenized in a Potter-Elvehjem homogenizer with 5 strokes of a drillpress-driven teflon pestle. Duplicate 3-ml. aliquots of whole liverhomogenates were added to tubes containing 2.1 ml. 5N NaOH andsaponified with 2.6 ml. 5N H₂ SO₄ and extracted twice with 5 ml. ofpetroleum ether (bp 40°-60° C.). Supernatants were added directly toglass counting vials, evaporated to dryness and 10 ml. oftoluene-PPO-POPOP scintillation fluid was added. Samples were analyzedfor absolute activity in a Packard Tri-carb scintillation counter.Resulting data was expressed as nanomoles ¹⁴ C-analine incorporated/gramof tissue/30 minutes.

    __________________________________________________________________________    Effect of oral administration of hydroxycitric acid                           derivatives (2.63 mmoles/kg) on                                               in vivo rates of lipogenesis.sup.1                                            __________________________________________________________________________    Formula I Derivative (2S,3S-                                                  configuration, unless otherwise                                               indicated).sup.2     Lipogenesis                                              __________________________________________________________________________                         nanomoles .sup.14 C-alanine/                                                              Percent                                      Y      R.sub.1                                                                            Z        g. liver/30 min.                                                                          Inhibition                                   __________________________________________________________________________           ASV           1022.4 ±                                                                         58.7(21).sup.3                                                                      0                                                   Saline        1027.3 ±                                                                         47.9(9)                                                                             0                                            CH.sub.3 O                                                                           CH.sub.3 CO                                                                        NH.sub.2 342.2 ±                                                                          133.6(4)                                                                            67                                           C.sub.2 H.sub.5 O                                                                    CH.sub.3 CO                                                                        NH.sub.2 683.1 ±                                                                          124.0(8)                                                                            33                                           C.sub.2 H.sub.5 NH.sub.2                                                             CH.sub.3 CO                                                                        OH       648.6 ±                                                                          104.9(7)                                                                            37                                           (C.sub.2 H.sub.5).sub.2 N                                                            CH.sub.3 CO                                                                        OH       858.8 ±                                                                          108.7(8)                                                                            16                                           (C.sub.2 H.sub.5).sub.2 N                                                            CH.sub.3 CO                                                                        CH.sub.3 O                                                                             684.9 ±                                                                          114.5(8)                                                                            33                                           C.sub.2 H.sub.5 O                                                                    CH.sub.3 CO                                                                        C.sub.2 H.sub.5 O                                                                      616.8 ±                                                                          70.9(7)                                                                             40                                           C.sub.2 H.sub.5 O                                                                    CH.sub.3 CO                                                                        C.sub.2 H.sub.5 NH                                                                     452.6 ±                                                                          128.2(5)                                                                            56                                           C.sub. 2 H.sub.5 O                                                                   CH.sub.3 CO                                                                        (C.sub.2 H.sub.5).sub.2 N                                                              446.7 ±                                                                          42.5(6)                                                                             56                                           C.sub.2 H.sub.5 O                                                                    CH.sub.3 CO                                                                        p-HOOC--C.sub.6 H.sub.4 --NH                                                           838.0 ±                                                                          228.5(4)                                                                            18                                           C.sub.6 H.sub.5 --CH.sub.2                                                           CH.sub.3 CO                                                                        OH       612.6 ±                                                                          96.1(5)                                                                             40                                           1-adamantyl                                                                          CH.sub.3 CO                                                                        OH       476.6 ±                                                                          63.5(7)                                                                             53                                           Formula IV - Ethyl 3(S),4(S)-4-                                               [N-(1-adamantylcarbamoyl)]-3-                                                 ethoxycarbonyl-3,4-dihydroxy-                                                                      566.1 ±                                                                          59.0(7)                                                                             45                                           butanoate                                                                     __________________________________________________________________________     .sup.1 Rats were prefasted 2 days and meal-fed the G-70 diet, for 7-13        days. They were given the derivatives (2.63 mmoles/kg) by stomach tube 60     minutes prior to feeding on the experimental day, and assayed in vivo         immediately after the meal.                                                   .sup.2 Derivatives were dissolved in ASV.                                     .sup.3 Mean ± SEM for the number of rats indicated in parentheses.         stomach tube 60 minutes prior to feeding on the experimental day, and     assayed in vivo immediately after the meal. .sup.2 Derivatives were     dissolved in ASV. .sup.3 Mean ± SEM for the number of rats indicated in     parentheses.

We claim:
 1. A compound of the formula ##STR7## wherein R₁ is loweralkanoyl; Y is NR₃ R₄ ; Z is OR₂ ; wherein R₂ is hydrogen; R₃ and R₄each taken independently is hydrogen, lower alkyl, monocyclic cycloalkylof 3 to 8 carbon atoms or 1-adamantyl;or an optical antipode or apharmaceutically acceptable salt thereof.
 2. The optical antipode of thecompound of claim 1 having the 2(S),3(S)-absolute configuration.
 3. Thecompound of claim 1 wherein R₁ is acetyl.
 4. The compound of claim 1which is tetrahydro-2-(N-ethylcarbamoyl)-3-acetoxy-5-oxo-furancarboxylicacid.
 5. The compound of claim 1 which istetrahydro-2-[N-(1-adamantylcarbamoyl)]-3-acetoxy-5-oxo-3-furancarboxylicacid.
 6. The compound of claim 1 which istetrahydro-2-(N,N-diethylcarbamoyl)-3-acetoxy-5-oxo-3-furancarboxylicacid.